Conventionally, a connection between nodes (switching units) constituting an ATM (Asynchronous Transfer Mode) network or a packet switching network is set up by a method such as PVC (Permanent Virtual Connection), SVC (Switched Virtual Connection), or SPVC (Soft Permanent Virtual Connection).
FIGS. 1 is a diagram showing an example configuration for illustrating a connection setup by PVC. In PVC, a network manager sets up connections by inputting setup commands from external input apparatuses 10a through 10d to ATM switching units 14a through 14d, respectively. This connection setup includes setting of connection management data such as port information, VPI (Virtual Path Identifier), VCI (Virtual Channel Identifier), cell rate, band, and service category.
The ATM switching units 14a through 14d each establishes a fixed connection based on the setup commands supplied from the external input apparatuses 10a through 10d, respectively. Set connection management data is maintained.
FIG. 2 is a diagram showing an example configuration for illustrating a connection setup by SVC. In SVC, message signal transmission and reception is performed between each connected ones of ATM switching units 18a through 18d so that the ATM switching units 18a through 18d store route information 20a through 20d, respectively. The connection setup is performed based on the route information.
For instance, a transmitting terminal 16a connected to the transmitting ATM switching unit 18a transmits a SETUP (a call connection request message) storing information such as address of a receiving terminal 16d, band information, and service category through a signal channel for signaling of the SETUP to the receiving terminal 16d connected to the receiving ATM switching unit 18d. 
In the case of normal connection, receiving the SETUP, the receiving terminal 16d transmits a CONNECT (a call connection confirmation message) to the transmitting terminal 16a and performs a connecting operation. Thus, according to SVC, a connection is established by a signaling signal that supports switching connection.
SPVC includes PVC and SVC. In SPVC, fixed connections are established between a transmitting terminal and a transmitting ATM switching unit and between a receiving terminal and a receiving ATM switching unit based on setup commands supplied from external input apparatuses. On the other hand, a connection is established between the transmitting and receiving ATM switching units by the transmitting ATM switching unit transmitting a SETUP to the receiving ATM switching unit and the receiving ATM switching unit thereafter transmitting a CONNECT to the transmitting ATM switching unit.
However, PVC requires the network manager to input the connection management data through the external input apparatuses 10a through 10d to the ATM switching units 14a through 14d, respectively, thus costing a lot of time.
In the case of SVC, it is not required to input the connection management data to each of the ATM switching units 18a through 18d. However, if a failure occurs on a network after the connections are established, all the connections set up with respect to the ATM switching units 18a through 18d are released as shown in FIG. 3.
In order to reestablish the connections, it is necessary to perform the connection setup from a stage of storing the route information 20a through 20d in the ATM switching units 18a through 18d. Therefore, SVC requires a predetermined period of time in each connection setup, thus taking time in failure recovery.
Further, as in SVC, it is also required in SPVC to perform the connection setup from the stage of storing the route information in each of the ATM switching units if all the connections are released due to a failure occurring on the network after the connections are established. In this case, there is a problem in that the connections are prevented from being established until the message signal transmission and reception is completed between each connected ones of the ATM switching units so that the route information is stored therein.